This invention relates to an improved process for phosphate flotation. In particular, this invention relates to the use of sulfonated aromatic hydrocarbons in the flotation of phosphate with a fatty acid and fuel oil.
In the present day commercial beneficiation of siliceous phosphate ores, a deslimed and sized phosphate ore is conditioned with and then floated by a fatty acid collector and fuel oil reagent in an aerated aqueous solution at a pH of at least about 8. This flotation process produces a low-grade phosphate concentrate containing from about 50 to 65 weight percent bone phosphate of lime (BPL). Frequently, the low-grade concentrate from the aforementioned flotation is blunged with acid to remove collector coatings, deslimed and the phosphate is further concentrated by flotation of residual silica from the concentrate with an amine-derived reagent.
The above described process is effective in the recovery of BPL from phosphate ore, but there exists a need for increased recovery of phosphate values without diminuation of the weight percent BPL in the concentrate. This need is exacerbated by the diminishing reserves of high-grade phosphate ore. In view of the large quantities of phosphate rock processed by froth flotation, such a development can result in a substantial increase in total amount of phosphorous values recovered.
Further, the present flotation agents have a limited tolerance for calcium, magnesium and like ions, present in the typically "hard" water used in the flotation medium. There exists a need for flotation agents which can tolerate a greater degree of "hardness" in the flotation medium.
As is illustrated in numerous patents, those skilled in the art have long sought a method to enhance the separation of phosphate values from silica in the phosphate ore. U.S. Pat. No. 3,164,549 discloses that dodecyl benzene sulfonic acid or certain other alkyl aryl sulfonic acids can be employed as a collector in preference to tall oil in a phosphate flotation process. The alkyl aryl sulfonic acid reagent, used at a loading of from 0.1 to 2 pounds reagent per ton of feed material, is disclosed to eliminate the need for a second flotation step to remove additional amounts of silica.
U.S. Pat. No. 3,292,787 teaches a process for beneficiating phosphate ores by froth flotation utilizing an alkali metal salt of a hydrocarbon aromatic sulfonic acid and a hydrocarbon oil of a specified viscosity.
Also known to the art, are certain partial esters of a polycarboxylic acid disclosed in U.S. Pat. No. 4,034,863, which are operable phosphate flotation agents. However, the aforementioned patented flotation processes have not been of commercial value. The limited increased phosphate recovery effected by these processes is more than offset by the higher cost of the reagents relative to those used in the conventional process.
The practice of this invention is useful to increase the recovery of phosphate in a froth flotation process without substantial diminution of the selectivity of the flotation.